A contraction or peristalsis of a smooth muscle for example of a digestive tract prevents a correct diagnosis upon an endoscopic test of a digestive tract such as a stomach or large intestine and allows a minute lesion such as a small-sized carcinoma to be missed.
As an anti-spasmodic agent upon an endoscopic test of a digestive tract, an anti-cholinergic agent scopolamine butylbromide (Trade name: Buscopan Injection, Nippon Boehringer Ingelheim Co., Ltd.) or glucagon has conventionally been prescribed. However, the scopolamine butylbromide is contraindicated in a patient having glaucoma, prostatic hypertrophy, arrhythmia and the like, and glucagon has a problematically low ability of inhibiting a gastric contraction.
In addition, some of these formulations involves a risk of causing ophthalmic regulatory failure or vertigo upon administration, and poses a problem in an individual receiving these formulations upon an endoscopic test because the individual should refrain for example from driving a car for a while after completion of the test.
Accordingly, in an attempt to solve the problems mentioned above, an investigation was made recently to produce a digestive tract contraction inhibitor using a peppermint oil whose main ingredient is L-menthol having a digestive tract contraction-inhibiting effect (GASTROINTESTINAL ENDOSCOPY, Vol. 53, No. 2, 172-177 (2001)). Nevertheless, a conventional formulation, which has been proposed to produce by mixing and stirring a peppermint oil and water in the presence of an homogenizer followed by allowing to stand at room temperature for a period of about one day and removing the oily component floating on the surface of the liquid to collect only a solubilized part, or by mixing and stirring a peppermint oil and water in the presence of an homogenizer followed by allowing to stand at room temperature for a period of 24 hours and then filtering the aqueous layer to remove the oily component, may allow a highly volatile L-menthol as a main ingredient of the peppermint oil to be evaporated off when allowed to stand at room temperature for several hours or longer after completion of the formulation, resulting in a reduced content, which may lead to a problematic non-uniform L-menthol content upon administration to patients. Accordingly, a constant amount of a conventionally-formulated product may fail to provide a constant effect even when administered for example by spraying as a gastric contraction inhibitor onto the inner wall of a stomach, resulting in an insufficient inhibitory effect on the contraction.
Furthermore, any of these products requires a preparation just before use because of a difficulty in storing for a prolonged period after the formulation, and such a preparation is difficult practically at each stage of the clinical medicine.
We had previously developed a digestive tract contraction inhibitor in an oil-in-water form exhibiting no L-menthol precipitation even after a prolonged storage by emulsifying the L-menthol as a main ingredient of a peppermint oil together with a fatty acid and/or a fat or oil using a surfactant. Nevertheless, some of these formulations is turbid, and such a turbid emulsion is concentrated onto a recess, groove or wrinkle, if any, on the surface of a digestive tract, when sprayed over such an inner wall, resulting in a problematic difficulty in observing a bottom or deeper end.
Under such a circumstance, development of a digestive tract contraction inhibitor having a reduced L-menthol volatility and an improved transparency, i.e., improved light transmittance, and also consisting of an emulsion which is stable for a prolonged period is highly desired.